Trench capacitors in SOI substrates

Abstract

A trench capacitor formed on an SOI substrate extends through an upper silicon layer and an insulating layer and into a semiconductor base substrate. The outer electrode of the trench capacitor includes portions of the semiconductor base substrate which bound the trench in which the trench capacitor is formed. The outer electrode is coupled to a contact structure formed in close proximity to the trench capacitor, and which extends through the insulating layer. The method for simultaneously producing the trench capacitor and contact structure includes forming two trench openings, forming a dielectric liner on one of the trench openings, then filling each of the trench openings with a semiconductor material.

What is claimed:  
     
       1. A semiconductor device comprising a trench capacitor formed on a silicon-on-insulator substrate, said silicon-on-insulator substrate including a silicon layer formed over an insulating layer formed over a semiconductor base substrate and including an upper surface being a top surface of said silicon layer, and said trench capacitor formed of a trench beginning at said upper surface and extending downward therefrom and through said silicon layer and said insulating layer and into said semiconductor base substrate, said trench capacitor including an oxide liner formed directly on and contacting sidewalls and a bottom surface of said trench, and a polysilicon plug formed within said trench and directly contacting said oxide liner. 
     
     
       2. The semiconductor device as in  claim 1 , wherein said oxide liner functions as the dielectric of said trench capacitor. 
     
     
       3. The semiconductor device as in  claim 1 , wherein said polysilicon plug forms a first electrode of said trench capacitor and portions of said semiconductor base substrate which bound said trench form a second electrode of said trench capacitor. 
     
     
       4. The semiconductor device as in  claim 3 , wherein said second electrode is further comprised of portions of said silicon layer which bound said trench. 
     
     
       5. The semiconductor device as in  claim 1 , wherein said polysilicon plug substantially fills said trench. 
     
     
       6. The semiconductor device as in  claim 1 , further comprising a contact structure including a semiconductor material formed within a further trench which extends downward from said top surface and through said insulating layer. 
     
     
       7. The semiconductor device as in  claim 6 , where in said contact structure is disposed laterally not more than five microns from said trench capacitor. 
     
     
       8. The semiconductor device as in  claim 6 , wherein said polysilicon plug substantially fills said trench and forms a first electrode of said trench capacitor, and said trench capacitor includes a second electrode being electrically coupled to said contact structure. 
     
     
       9. The semiconductor device as in  claim 8 , wherein said second electrode comprises portions of said semiconductor base substrate which bound said trench. 
     
     
       10. The semiconductor device as in  claim 6 , wherein said contact structure comprises polysilicon formed within said further trench. 
     
     
       11. The semiconductor device as in  claim 1 , wherein said polysilicon plug forms a first electrode of said trench capacitor, and 
       further comprising a second electrode of said trench capacitor comprising portions of said silicon layer which bound said trench.  
     
     
       12. The semiconductor device as in  claim 11 , further comprising a dielectric film formed over said silicon layer and said trench capacitor, said dielectric film including a first contact opening which provides for contacting said first electrode and a second contact opening which provides for contacting said silicon layer. 
     
     
       13. A semiconductor device comprising a trench capacitor formed on a silicon-on-insulator substrate, said silicon-on-insulator substrate including an undoped silicon layer formed over an insulating layer formed over a semiconductor base substrate, and said trench capacitor extending through said undoped silicon layer and said insulating layer and into said semiconductor base substrate. 
     
     
       14. The semiconductor device as in  claim 13 , wherein said trench capacitor is formed of a trench which begins at a top surface of said undoped silicon layer and extends downward therefrom, and further comprising a contact structure including a semiconductor material formed within a further trench which extends downward from said top surface and through said insulating layer. 
     
     
       15. The semiconductor device as in  claim 13 , in which said trench capacitor includes an oxide liner formed directly on and contacting sidewalls and a bottom surface of a trench extending through said undoped silicon layer and said insulating layer and into said semiconductor base substrate, and a polysilicon plug formed within said trench and directly contacting said oxide liner, which serves as the dielectric of said trench capacitor.